I see no problem at all with what you posted. What exactly is the problem?
Mining isnt a flat line, you may just think that because some pools do smoothing on the curves so that it looks nicer.
For example:
bitcoin miner:

ZEC mining:

ETH mining:

Correct, it really depends on the pool that you are using on how they do visualize the mining stats and i didnt even see about that flat line, maybe its just an another setting of the chart that you mean. Zig-zag would be always noticeable and its a good indication and besides mining difficulty does increase which means hashes or profits would be more lesser and lesser.